Stucco finishes are an example of an exterior finish that has been used since ancient times. Still widely used throughout the world, stucco exterior finishes make up one of the most common ways of finishing exteriors of both residences and commercial buildings.
Like interior wall plaster, stucco has traditionally been applied on exterior surfaces as a multiple-layer process, sometimes consisting of one, two, but more commonly as three coats. Whether applied directly to a masonry substrate or onto wood with a metal lath, the process of applying stucco includes the step of applying a first “scratch” or “pricking-up” coat, followed by a second coat, sometimes referred to as a “floating” or “brown” coat, followed finally by the “finishing” coat. Up until the late-nineteenth century, the first and the second coats were of much the same composition, generally consisting of lime, portland cement, sand, perhaps clay and one or more other natural additives. Straw or animal hair was usually added to the first coat as a binder.
The third, or finishing coat, consisted primarily of a very fine mesh grade of lime and sand, and sometimes a color pigment.
Although traditional stucco finishes have been used on building exteriors for quite some time, traditional stucco finishes have their limitations. Those limitations include porosity, rigidity, freeze/thaw fractures, fungal and mildew formation, cracking, complexity of installation, high maintenance and the requirement for a specialized skilled labor pool to properly apply the stucco finish so that it will both look good and withstand the effects of weather.
Because modern synthetic stucco finishes are watertight, any water that remains trapped behind these modern synthetic stucco finishes does not readily evaporate. The trapped water behind the stucco finish can then soak into the substrata and framing of the building. The water that soaks into the substrata and framing often causes severe damage to the building without any signs of damage appearing on the exterior of the building. These problems can exist regardless of the age of the building or the quality of construction. Another problem leading to severe damage is insulation cladding. Specifically, insulation cladding is unforgiving for water penetration or condensation. Moreover, the durability of the cladding itself is prone to penetration by abrasion, birds, insects and airborne debris.
Although modern synthetic stucco finishes are attractive and long lasting, their usefulness is compromised by the integrity of the foundation to which it is applied. It has been found that one of the most durable foundations for a direct applied synthetic stucco finish is formed by either engineered treated wood panels, cement panels or fiber cement panels affixed either to the exterior sheathing or directly to the building frame.
The recent introduction of engineered treated wood panels, cement panels, and fiber-cement panels, available in 4-foot widths by various lengths and thickness, has provided an opportunity to replace prior art stucco systems with a preformed exterior wall panel that can be installed like wood paneling or interior drywall panels. However, just like interior drywall panels, exterior wall panels, when installed, have seams or joints between each panel that must be filled so that a smooth exterior finish may be applied.
To create a pleasing and uniform appearance for the exterior of a building, the outline of each wall panel should be invisible. For interior drywall panels, hiding the outline of each panel is achieved by tapering the edges of the panels so that when the drywall panels abut one another, the tapered edges provided a channel suitable for the use of tape and mud to hide the resulting seams. The process of first taping and then placing mud over the tape creates a smooth transition between panels. Unfortunately, unlike interior drywall panels with their tapered edges, exterior wall panels typically lack tapered edges and do not form a channel which is easily filled and masked. Hence, when exterior wall panels are placed along side one other on the exterior of a building, a butt-joint with square edges is created. This butt-joint between the exterior wall panels is difficult to disguise. In addition, the edges of each wall panel are subject to the stresses of building movement, temperature changes and other environmental factors. Accordingly, the foregoing factors must be considered when finishing an exterior wall so that no seams or joints between exterior wall panels are visible.
One prior art solution, described in U.S. Pat. No. 6,516,580, teaches simply filling the gaps between exterior fiber cement panels with a polyurethane caulk. The polyurethane caulk is then covered with a 3-inch wide, peal and stick butyl-rubber tape having a fabric backing. This butyl-rubber tape and the rest of the panel is then coated with an exterior synthetic stucco finish coat. This solution has proven to be unsatisfactory because it overlooks the problems of out-gassing from the polyurethane caulk. Specifically, if the polyurethane caulk isn't fully cured due to time or climate constraints and is then covered by a non-permeable butyl rubber tape, the emission of gas from the polyurethane caulk causes blisters or ridges to form as the trapped gas tries to escape (out gas) from the polyurethane caulk. In addition, there is also a tendency for the butyl-rubber tape to “blister” if any air becomes trapped while handling and applying the butyl-rubber tape to the panel. Furthermore, the butyl-rubber tape is extremely tacky and has a tendency to stick to itself during application creating a tenting effect that bulges outwardly from the butt-joint between the exterior wall of the fiber cement panel. Moreover, peel & stick tapes have a tendency not to stick well in in cold or freezing temperatures as well as to edge creep causing visible cracks to telegraph through to the stucco finish outlining the edges of the peel and stick tape.
The prior art approach of placing butyl-rubber tape over a polyurethane caulk overlooks the problem presented by a butt-joint between exterior fiber cement panels. By sealing the polyurethane caulk with a butyl-rubber tape, an elevation is created at the seams between the fiber cement panels. This elevation accentuates the outline of the panels. Flexibility at the butt-joint between the fiber cement panels is then compromised. To address the problem of accentuating rather than hiding panel outlines, applicators have attempted to place multiple layers of stucco over the exterior fiber cement panels. These multiple layers of stucco increase the material and labor cost. Moreover, any irregularities still evident after the stucco finish is applied will be very difficult, if not impossible, to hide. Accordingly, there still remains a need in the art for a system and method for filling the space between exterior wall panels that provides a smooth appearance for painting or the application of a stucco finish.
Another prior art patent, U.S. Pat. No. 7,159,368, also describes the use of an elastomeric joint tape made with an elastomeric backing material, with the option of an optional release liner laminated to the adhesive.
Further research has revealed the potential for hairline cracks at joints and seams given the issues of building settlement, stud movement, incorrect panel nailing and attachment, and other problematic construction practices. Upon further study, it was also determined that the over-application of ceramic spackle such as the Fill-N-Build product marketed by Global Coatings, Inc. at panel field joints could also contribute to hairline cracking. Moreover, the use of a reinforced joint tape along a mastic such as the AcraCream product marketed by Global Coatings, Inc. as the sole factor to seal, waterproof and manage joint movement could be improved. Given the soft flexible nature of the mastic, the joint tape and a primer such as the ColorFlex product marketed by Global Coatings, Inc., tethered by direct interface to relatively hard synthetic stucco finish such as the Carrara product marketed by Global Coatings, Inc., the potential for hairline cracks in the synthetic stucco finish would be enhanced by the flexing of the relatively softer and more flexible joint treatment components. It became clear that given the wide issues of building envelope movement as well as freeze/thaw associated with weathering, there remains a need in the art for a more forgiving and accommodating joint treatment system to provide a basis for the creation of a true non-cracking finish and stucco system usable on various types of exterior wall panels.